Dispenser for dry application of polyacrylamide

ABSTRACT

An apparatus dispenses dry polyacrylamide (PAM), which is very sensitive to humidity, into irrigation water for stabilizing soil to reduce erosion and maintain porosity. A tank containing PAM discharges the PAM into a feed tube leading to a distribution canister. A fan at the canister blows a stream of air across an outlet end of the feed tube to keep moist air away from the end of the tube and facilitate discharge of the PAM into the canister and out of the open bottom end of the canister into the irrigation water. The apparatus is battery powered for use in remote areas without power lines and is operated periodically by a programmable timer.

FIELD OF THE INVENTION

This invention relates to a dispensing apparatus for dispensing drypolyacrylamides in irrigation ditches or furrows for soil stabilizationand improved irrigation.

BACKGROUND OF THE INVENTION

In agricultural areas where fields are irrigated by running water intofurrows, erosion of the soil is a major problem. While furrow irrigationhas significant advantages including water saving and less costlyequipment, especially as compared with overhead sprinklers, it also hassome disadvantages. In particular, furrow or ditch irrigation causessignificant soil erosion as the water running along the furrow washesaway soil. In some areas, erosion of topsoil can amount to between 2.8and 28 tons per acre during a 24 hour watering interval.

In addition, this form of irrigation can remove valuable pesticides andfertilizers which become pollutants in the waterways to which they run,and the soil itself can become less porous, and therefore less able toaccept the irrigation water and convey it to plant roots, as fine clayparticles settle out of the water and clog soil pores.

It has been found that certain polyacrylamides (PAMs) greatly alleviatethese problems and make furrow irrigation a useful and much lessdestructive irrigation technique, extending the useful life of manyacres of farmland. PAMs are long-chain polymers, also used to cleanwaste water, which reduce the amount of soil carried by the irrigationwater and reduces the negative effect of the erosion on soil porosity.Although the mechanism by which this is accomplished is not fullyunderstood, its effectiveness is widely acknowledged.

PAMs are employed in furrow irrigation by adding selected quantities ofthe substance in a powder-like form to the irrigation water as the wateris dispensed or flowed into the field. Unfortunately, before thematerial is added to the irrigation water, it is highly sensitive tomoisture, particularly moisture in the air, i.e., humidity. When the drypolymer is exposed to moisture, it tends to become sticky andagglomerates. As the amount of moisture increases, the substance becomesincreasingly sticky and no longer flows as a powder. Any attempt tosimply dispense the PAM through a tube under humid conditions results inthe tube being blocked by agglomerated PAM in a short interval of time.

This becomes important because the PAM must be dispensed over andadjacent to the surface of the irrigation water in order to prevent itfrom being blown away and lost, a dispenser being held as close as oneinch to, or as far away as one foot from, the water surface. Theproximity of the dispenser to the water creates humidity where it isleast wanted, in the dispensing tube.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an apparatus fordispensing polyacrylamide in dry form to irrigation water.

A further object is to provide such an apparatus which dispenses PAMwhile greatly reducing the agglomerating effect of humidity on the PAMas it is being dispensed.

Yet another object is to provide such a dispensing apparatus which isoperable at locations remote from a conventional power source for longintervals of time.

Briefly described, the invention comprises van apparatus for dispensingdry polyacrylamide into a body of water comprising the combination of acanister having an open end and means for supporting the canister over abody of water with the open end facing the water. A supply container ofdry polyacrylamide is supported above the canister and a feed tubeextends from the supply container to the canister, the feed tube havingan outlet end in the canister. Polyacrylamide is discharged from thecontainer into the feed tube. Means including a fan blows a stream ofair past the outlet end of the feed tube to blow humid air away from theoutlet end and to facilitate discharge of dry polyacrylamide from thefeed tube into the canister and through the open end thereof to the bodyof water.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to impart full understanding of the manner in which these andother objects are attained in accordance with the invention,particularly advantageous embodiments thereof will be described withreference to the following drawings, which form a part of thisdisclosure, and wherein:

FIG. 1 is a front elevation of an apparatus in accordance with theinvention;

FIG. 2 is a side elevation of the apparatus of FIG. 1;

FIG. 3 is a top plan view of the apparatus of FIGS. 1 and 2;

FIG. 4 is an enlarged, partially cut away front elevation of a portionof the apparatus of FIGS. 1-3;

FIG. 5 is an enlarged partial side elevation, in partial section, of adispensing portion of the apparatus of FIGS. 1-3;

FIG. 6 is a simplified view similar to FIG. 5 in outline only to showair flow patterns therein during operation; and

FIGS. 7 and 8 are simplified side elevations, in section, of furtherembodiments of the invention usable under relatively low humidityconditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1-3, which show the general organization of theapparatus, a frame indicated generally at 10 is preferably made of 1.5"angle iron and has legs 12 which are adjustable in length so that thetop of the frame can be positioned a desired distance above a supportingsurface 13, typically the surface of the earth adjacent an irrigationditch 11. The top portion 14 of frame 10, which is normally about 2 feetto 3 feet above the surface, supports part of the components of theapparatus for dispensing PAM.

A supply tank 15 is supported above frame top 14 on brackets 16. Tank 15contains a supply of the PAM to be dispensed, typically about 70 lbs.,and is closed to prevent the entry of moisture. At the bottom of tank 15is an impeller 13, (FIG. 3), which is of a conventional type commonlyused to feed granular, particulate or powdery material from a tank orhopper such as in apparatus for discharging fertilizer or the like. Theimpeller is driven by a shaft 17 which is rotatably supported in one ofthe tank support brackets 16 and, when the impeller is turned, thepowder-like PAM material from the tank passes downwardly through a feednipple 18 at the bottom of the tank.

A 12 volt DC gearhead motor 20 is supported above frame top 14 on abracket 22, the output shaft of the motor gearhead being connected toone end of a shaft 19 which is rotatably supported in two bearings 23.Shaft 19 extends to the opposite side of table 10 from motor 20 andcarries a chain sprocket 25 attached thereto. A chain 27, such as aconventional bicycle chain, passes around sprocket 25 and anintermediate sprocket 28 on an idler shaft 29 which also carries asprocket 30, shown most clearly in FIG. 4. A second, similar chain 32passes around sprocket 30 and drives a larger sprocket 33 mounted onshaft 17. Thus, rotation of motor 20 causes rotation of the tankimpeller at a somewhat slower speed, causing PAM material from the tankto be dispensed therefrom through nipple 18 and a short section offlexible hose 35.

A feed tube 37 is connected to hose 35 by a 45° elbow 39 and carries PAMmaterial from the tank to a dispenser indicated generally at 40. Thedispenser is shown more clearly in FIGS. 5 and 6, FIG. 5 showing themechanical structure of the canister and FIG. 6 showing the flow of airand material therein. Dispenser 40 includes a cylindrical canister 42which is in the shape of an inverted can about 6" in diameter, closed atthe top and open at the bottom. Feed tube 37 passes through thecylindrical wall of canister 42 near the top of the canister andterminates at an open end about 2" inside canister 42. It is importantfor canister 42 and the associated pipes, etc., to be made of anon-metallic, material having low thermal conductivity, preferably aplastic material such as polyvinyl chloride (PVC), to minimize theamount of condensation on those components.

As best seen in FIG. 5, a cylindrical fan housing 44, also made of PVC,is attached to an opening through a side of canister 42 such that theinteriors of canister 42 and housing 44 are open to each other and sothat the axes of the canister and housing are at an angle of about 45°from each other. A 12 volt DC brushless fan 46 is mounted in housing 44,the fan being connected so that it draws air in through a D-shapedopening 45 through the wall of housing 44 and also from within canister42. Fan 46 is about 4" in diameter. A reducer 47 receives air from thefan and delivers it into a sequence of short pipes and elbows,collectively identified as 48, which reverses the flow of air byslightly more than 180° and delivers a flow of air from an outlet end 50which enters canister 42 near the top thereof and delivers a flow of airfrom above and passing the outlet end of feed tube 37.

On the outside of canister 42 is a semi-cylindrical mounting sleeve 52having vertically elongated slots 54 on opposite sides of canister 42through which screws 55 pass to attach the sleeve to canister 42,permitting vertical adjustment of sleeve 52 relative to the canister. Atthe ends of sleeve 52 are radially outwardly extending ears 56 and atthe bottom of sleeve 52 and ears 56 are oppositely extending mountingflanges 57. Flanges 57 can be used to mount dispenser 40 on a supportspanning an irrigation ditch 11 and the adjustment provided by screws 55and slots 54 permit a user to establish the height of the dispenserrelative to the surface of the irrigation water in the ditch.

A plurality of tubes 59 are fixedly attached to opposite sides of theouter surface of canister 42 to provide alternative mountingcapabilities.

A programmable 12 volt DC controller 60 is mounted on frame 10 and iselectrically connected to motor 20 and the motor of fan 46. A 12 voltbattery 62, such as a high ampere-hour automotive battery, is alsoprovided and can be mounted on the frame or placed at any convenientlocation. The battery is particularly important because the apparatusdescribed herein is intended to be used at locations where no electricalservice is available, i.e., at locations in a farm field. A solar panel64 can also be provided with suitable circuitry to recharge the battery.However, motor 20 requires 1.1 amperes and the fan requires about 0.16amperes, a total of 1.26 amperes. Thus, the apparatus can be operatedfor about 85 hours from a 105 ampere-hour battery without recharging.This provides considerable time for irrigating, the actual time in daysdepending on the number of hours of irrigation each day.

Controller 60 can be a rather simple device, preferably using solidstate devices, for controlling the operation of the motors. It includesa clock and switches for energizing the motors at selected times and isalso capable of changing the speed of motor 20 from full speed to alower sustaining rate. The technique preferably used in this form ofirrigation is to dispense a selected rate of PAM into the water for atime sufficient to permit the water to flow to the end of the irrigationditch. By that time, the PAM has coated the surfaces of the ditch andthereafter, for the remainder of this irrigation treatment, it is onlynecessary to dispense a smaller amount of PAM into the water, typicallyabout 10% of the initial rate. Motor 20 is therefore slowed to aconsiderably lower speed, reducing the dispensing rate. The on and offtimes for the motors can be selected as well as the time for changingthe motor speed, based on the length of the field to be irrigated.

It is also possible to change the motor drive sprockets. Normally,appropriate sizes for the sprockets are initially chosen on the basis ofthe acreage of field to be irrigated and would not be changed again forthat specific installation. However, it is important to be able tochange the sprockets to different drive ratios so that the levels of PAMbeing dispensed are suitable for the field size and amount of waterbeing used per unit time. For a larger than normal installation, it maybe necessary to drive sprocket 33 on shaft 17 directly from sprocket 23on shaft 19, thereby eliminating the idler sprockets entirely.

FIG. 6 illustrates the function of the fan and the general pattern ofair flow which keeps the PAM from agglomerating and clogging feed tube36. When the process begins, the air in and under the open end ofcanister 42 is the most humid air, symbolized by the open arrows 65. Fan46 draws outside air, symbolized by the line arrows 66, in throughopening 45 and also from canister 42, drawing humid air away from theoutlet end of tube 37. That air is propelled by the fan through pipe 48and past the open end of feed tube 37, blowing the humid air away fromthe feed tube and drawing PAM, symbolized by the small circles 67,dispensed from tank 15 into canister 42 where it falls through thebottom of the canister into the irrigation water. The air propelled bythe fan thus prevents agglomeration and also has an aspirating effect topropel the PAM powder into the canister. Efforts to accomplish the samething without fan 46 and pipe 48 resulted in the outlet end of tube 37being blocked in a few minutes of operation.

In an alternative arrangement, not illustrated, which proved to besatisfactory and has some manufacturing advantages, a hole is madethrough the elbow leading to outlet end 50 and tube 37 is passed throughthat opening so that the outlet end of tube 37 is essentially concentricwith outlet end 50. The stream of air thus surrounds the materialemerging from tube 37, the end of which is recessed a small distancebehind end 50 with respect to the direction of air flow.

It is believed that the operation and manner of use will be apparentfrom the foregoing description. However, the operation can be summarizedas follows.

The apparatus is positioned adjacent an irrigation ditch as illustratedin FIGS. 1-3. The ditch may be a ditch leading directly to the crops tobe irrigated or may be a ditch feeding other irrigation ditches alongwhich crops are planted. The timer is set to commence irrigation at aselected time each day, to reduce the speed of motor 20 at a certaintime after starting, and to stop feeding material at a selected time,coordinated with the desired irrigation times. The interval of timebefore reduction of motor speed may need to be determined experimentallyand will depend on the size of the area being irrigated, recognizingthat an entire farm of several fields may be treated from one dispenser.At the selected time, water is fed into the system and the timer turnson, commencing rotation of shaft 17 by motor 20 to discharge PAM fromtank 15. At the same time, fan 46 commences air flow through pipe 48,reducing the humidity at the outlet end of tube 37. The PAM isdischarged from tube 37 and falls into the irrigation water as it passesunder dispenser 40, producing the desired effect.

Alternative embodiments which are usable only in low humidity conditionsare shown in FIGS. 7 and 8. The portions of the apparatus not shown arethe same as discussed above. In the embodiment of FIG. 7, a dispensingcanister 70 is shown in a simplified sectional view. Feed tube 37 entersthe canister as with the embodiment of FIGS. 5 and 6. An air streamhousing 72 is mounted on the top of housing 70 and contains a fan 72which draws air in from the outside above the canister and blows astream of air out of an outlet end 76 which passes the outlet end of thefeed tube, assisting with the dispensing of PAM particles.

The embodiment of FIG. 8 includes a housing 80 with a fan 82 mounted inthe top thereof. Feed tube 37 enters the canister as described above.The fan blows downwardly, assisting in the dispensing of material intothe irrigation water. Again, the embodiment of FIG. 8 is not effectivein high humidity conditions for the reasons discussed above.

While certain advantageous embodiments of the invention have beendescribed in detail, it will be apparent to those skilled in the artthat various changes and modifications can be made therein withoutdeparting from the scope of the invention as defined by the appendedclaims.

What is claimed is:
 1. An apparatus for dispensing dry polyacrylamide into a body of water comprising the combination ofa canister having an open end; means for supporting said canister over a body of water with said open end facing said water; a supply container of dry polyacrylamide; a feed tube extending from said supply container to said canister, said feed tube having an outlet end in said canister; means for discharging polyacrylamide from said container into said feed tube; means including a fan for blowing a stream of air past said outlet end of said feed tube to blow humid air away from said outlet end and to facilitate discharge of dry polyacrylamide from said feed tube into said canister and through said open end thereof to said body of water.
 2. An apparatus according to claim 1 wherein said means for blowing includes a fan housing connected to said canister and having a fan therein, means defining an opening through said fan housing to admit outside air so that said fan draws air into said fan housing from the outside and from said canister, and a duct from said fan to a location adjacent said outlet end of said feed tube to supply said stream of air.
 3. An apparatus according to claim 2 wherein said canister, said fan housing and said duct are made of a non-metallic material to minimize condensation of moisture thereon.
 4. An apparatus according to claim 1 wherein said means for discharging includesrotatable means in said supply container for causing said dry polyacrylamide to leave said tank through a bottom exit opening; a drive shaft connected to drive said rotatable means; a direct current motor operable at at least two speeds connected to drive said shaft; and a timer connected to said fan and to said motor to operate said motor at a first speed for a first selected interval of time and at a second speed lower than said first speed for a second selected interval of time to thereby dispense polyacrylamide at a first rate for said first interval and at a second lower rate for said second interval.
 5. An apparatus according to claim 4 and including a storage battery connected to said timer to provide electrical power to said timer, said fan and said motor.
 6. An apparatus according to claim 5 and including means for recharging said battery. 